SM3 Crankcase Ventilation Issue

Good day, esteemed Renault SM3 owner. Your description certainly suggests a crankcase ventilation malfunction. The symptoms you are experiencing, namely the check engine light, reduced power, and smoke upon acceleration, align with a defective PCV (Positive Crankcase Ventilation) system. Have you observed any unusual idling behavior, such as a rough or fluctuating idle speed? Furthermore, have you inspected the PCV valve and its associated hoses for any visible signs of leaks or damage?

Thanks for the quick reply! Regarding the idling, yes, it's been a little rougher than usual, sometimes dipping lower than it should. As for checking the valve and hoses myself, could you give me a little more detail about where exactly I should be looking, and what kind of damage I should be trying to spot? I'm reasonably handy, but I don't want to start pulling things apart without some guidance.

Understood. Given the reported rough idling in conjunction with the other symptoms, a faulty crankcase ventilation valve remains the most probable cause. While a visual inspection of the valve and hoses for cracks or looseness can provide preliminary insight, a comprehensive diagnosis often necessitates specialized tools and expertise. Therefore, I strongly advise that you seek the services of a qualified automotive technician. Continued operation with a malfunctioning crankcase ventilation system may lead to more severe engine damage. It would be best to take your vehicle to a reputable workshop for a thorough inspection and appropriate repairs.

Thanks a lot for the advice! I took it to my local mechanic, and you were spot on – it was indeed the crankcase ventilation valve. They replaced it, and the total cost came to about 360€. The car is running much better now, no more smoke, and the check engine light is gone. Really appreciate your help in pointing me in the right direction!